How to establish link between FI and MM modules?

Folks, I am new to BW and have a question regarding preparing Tech Design Docs in my current project. How can we link between FI-GL (0fi_gl_04) and Billing/orders in MM (2lis_13_vdkon/2lis_11_vaitm). Basically I am trying to figure out what are the key fields we meet to match to make sure the data is extracted properly. Any help is appreciated. Thanks in advance. Below are some fileds if that might help in answering.

company code

business area

material number

from plant

cost center

sales district

sales group

pack size

sales doc type

distribution channel

Thx

Neal